As a representative example of a conventional boiling water reactor (BWR), which has been put into practical use, there is known an advanced BWR (ABWR). Hereinafter, an outline of structures of a containment vessel and the like of the ABWR will be described with reference to FIG. 6 (see Patent Document 1, etc.)
In FIG. 6, a core 1 is accommodated inside a reactor pressure vessel (RPV) 2. A containment vessel (CV) 3 includes a cylindrical side wall (tubular side wall) 4, a top slab 5 closing an upper portion of the cylindrical side wall 4, a containment vessel head 6 provided at a center portion of the top slab 5, and a base mat 7 supporting the above components and closing a lower portion of the cylindrical side wall 4. The above components are designed so as to withstand a pressure rise upon occurrence of a design basis accident and constitute a pressure boundary. An inner space of the containment vessel 3 is partitioned into a dry well (DW) 8 accommodating the reactor pressure vessel 2 and a suppression chamber (wet well) (WW) 9.
The reactor pressure vessel 2 is supported by a vessel support 10 through a vessel skirt 11. A part of a space inside the dry well 8 above the vessel skirt 11 is referred to as an upper dry well 12, and a part of the space inside the dry well 8 below the vessel skirt 11 is referred to as a lower dry well 13. The suppression chamber 9 is installed so as to circumferentially surround the lower dry well 13 and has, inside thereof, a suppression pool (ST) 14. The dry well 8 and the suppression pool. 14 are connected to each other by vent pipes 15.
The dry well 8 and the wet well 9 have an integral structure having a cylindrical shape to constitute the containment vessel 3. A horizontal floor separating the dry well 8 and the wet well 9 from each other is referred to as a diaphragm floor 16. The containment vessel 3 has a design pressure of 3.16 kg/cm2 in gauge pressure. The cylindrical side wall 4 and the top slab 5 are formed of reinforced concrete with thicknesses of about 2 m and about 2.4 m, respectively. Inner surfaces of the cylindrical side wall 4 and the top slab 5 are each lined with a steel liner (not illustrated) for the purpose of suppressing leakage of radioactive materials. The base mat 7 is formed of reinforced concrete with a thickness of about 5 m.
In FIG. 6, an edge line of the cylindrical side wall 4 representing a joint part between the cylindrical side wall 4 and the top slab 5 is extended to a topmost potion of the containment vessel 3 for making a boundary therebetween easy to understand. Actually, there may be a case where the top slab 5 is placed on the cylindrical side wall 4. Alternatively, since both the cylindrical side wall 4 and the top slab 5 are formed of reinforced concrete, there may be a case where the joint part between the cylindrical side wall 4 and the top slab 5 constitutes a common part (continuous structure) to make the boundary obscure. The containment vessel in which the primary structures are formed of reinforced concrete is generally referred to as RCCV.
The containment vessel head 6 is formed of a steel so as to be capable of being removed upon refueling. Recently, there exists a type in which a water shield pool (not illustrated) is arranged above the containment vessel head 6. Further, recently, there exists a type in which a cooling water pool (not illustrated) of a passive safety system is arranged above the top slab 5. A design leak rate of the containment vessel 3 is about 0.5%/day
In recent years, a plan is being studied in which the cylindrical side wall 4 and the top slab 5 are each not formed of the reinforced concrete but of a steel concrete composite (SC composite). The SC composite is obtained by filling concrete between two steel plates. The use of the SC composite eliminates the need of laying rebar and allows module construction. There is known, as an example in which the SC composite is adopted to a nuclear power plant, a shield building of AP1000 made by Toshiba/Westinghouse.